diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 5ffe433746..7fe00cb45a 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -1337,10 +1337,14 @@ class Formula
     end
   end
 
-  # Clear caches of .racks and .installed.
-  # @private
-  def self.clear_cache
+  # Clear cache of .racks
+  def self.clear_racks_cache
     @racks = nil
+  end
+
+  # Clear caches of .racks and .installed.
+  def self.clear_installed_formulae_cache
+    clear_racks_cache
     @installed = nil
   end
 
diff --git a/Library/Homebrew/tab.rb b/Library/Homebrew/tab.rb
index 1cabacefdd..3bb7d8b624 100644
--- a/Library/Homebrew/tab.rb
+++ b/Library/Homebrew/tab.rb
@@ -317,6 +317,10 @@ class Tab < OpenStruct
   end
 
   def write
+    # If this is a new installation, the cache of installed formulae
+    # will no longer be valid.
+    Formula.clear_installed_formulae_cache unless tabfile.exist?
+
     CACHE[tabfile] = self
     tabfile.atomic_write(to_json)
   end
diff --git a/Library/Homebrew/test/keg_test.rb b/Library/Homebrew/test/keg_test.rb
index fdc739c9d8..2c91027e5b 100644
--- a/Library/Homebrew/test/keg_test.rb
+++ b/Library/Homebrew/test/keg_test.rb
@@ -327,7 +327,6 @@ class InstalledDependantsTests < LinkTests
     f = stub_formula_name(name)
     keg = super
     Tab.create(f, DevelopmentTools.default_compiler, :libcxx).write
-    Formula.clear_cache
     keg
   end
 
diff --git a/Library/Homebrew/test/uninstall_test.rb b/Library/Homebrew/test/uninstall_test.rb
index 70a6943531..06b067886b 100644
--- a/Library/Homebrew/test/uninstall_test.rb
+++ b/Library/Homebrew/test/uninstall_test.rb
@@ -34,13 +34,11 @@ class UninstallTests < Homebrew::TestCase
   end
 
   def test_check_for_testball_f2s_when_developer
-    skip "Flaky test"
     assert_match "Warning", handle_unsatisfied_dependents
     refute_predicate Homebrew, :failed?
   end
 
   def test_check_for_dependents_when_not_developer
-    skip "Flaky test"
     run_as_not_developer do
       assert_match "Error", handle_unsatisfied_dependents
       assert_predicate Homebrew, :failed?